Conventionally, in order to slow a rotational speed of a rotary body such as a door, a lid, a handle (a grip handle), and the like rotatably supported relative to a base, there is used a rotary damper (for example, Patent Documents 1 and 2). The rotary damper includes a housing in which a viscous fluid is enclosed inside thereof, and a rotor including a blade portion rotatably housed inside the housing (for example, the Patent Document 1). The housing is connected to one of either the base or the rotary body, and the rotor is connected to the other of either the base or the rotary body. When the rotary body rotates relative to the base, the rotor rotates relative to the housing, and due to a fluid resistance (an internal frictional resistance) of the viscous fluid, there is generated a braking torque between the rotations of the rotor and the housing so as to slow the rotation of the rotary body relative to the base.
The rotary damper according to the Patent Document 1 comprises the housing including an outer cylinder having a predetermined axis line, an inner cylinder disposed coaxially inside the outer cylinder, and a bottom plate closing one end side in an axis line direction of the outer cylinder and the inner cylinder, wherein an annular liquid chamber is defined by the outer cylinder, the inner cylinder, and the bottom plate; and the rotor including the cylindrical blade portion rotatably received in the liquid chamber coaxially with the outer cylinder. O-rings having flexibility are interposed respectively between a rotor shaft and the outer cylinder, and between the blade portion and the inner cylinder, and the rotor and the housing are rotatably sealed. A control of a movement in a rotational axis line direction of the rotor relative to the housing, i.e., a prevention of the rotor from coming out of the housing, is carried out by locking one of either the rotor or the housing in a locking portion formed in the other of either the rotor or the housing.